Yes, this is a condition of your rental, unlock the cable from the parking stand and then lock the bike securely with the cable at the end of your journey. Use it too when you are taking a break during your rental.
You should always lock a Moby bike when you are leaving it unattended as losing the bike will incur a penalty and makes you liable for the cost of the bike in case of a theft.
For Moby Pedal bikes, put the cable over a Sheffield stand and use the loose end to go through the lock.
You have to make sure that the bike is parked correctly and that it is not obstructing the paths of pedestrians or other vehicles. IT IS NOT ALLOWED TO LOCK ON POLES, FENCES, LAMP POSTS, RAILINGS OR LEFT UNLOCKED.